Migraine is a complex, common neurological condition that is characterized by severe, episodic attacks of headache and associated features, which may include nausea, vomiting, sensitivity to light, sound or movement. In some patients, the headache is preceded or accompanied by sensory warning signs or symptoms (i.e. auras). The headache pain may be severe and may also be unilateral in certain patients. Migraine attacks are disruptive to daily life and cost billions of dollars each year in missed work days and impaired performance (Modi and Lowder, Am. Fam. Physician, Vol. 73:72-78, 2006).
Migraine is a highly prevalent disease worldwide with approximately 15% of the European population and 12% of the United States population suffering from migraine attacks (Lipton et al, Neurology, Vol. 68:343-349, 2007). Additionally, migraines have been found to be associated with a number of psychiatric and medical comorbidities such as depression and vascular disorders (Buse et al., Neurol. Neurosurg. Psychiatry, Vol. 81:428-432, 2010; Bigal et al., Neurology, Vol. 72:1864-1871, 2009).
Migraine headache is commonly treated acutely, primarily with analgesics and a class of drugs called triptans (Humphrey et al. Ann NY Acad Sci., Vol. 600:587-598, 1990; Houston and Vanhoutte, Drugs, Vol. 31:149-163 1986). The triptans, which are selective serotonin 5-HT1B/1D agonists, are effective drugs for acute migraine and are generally well tolerated, but are contraindicated in the presence of cardiovascular disease due to their potential for coronary vasoconstriction. In addition, many migraine patients do not respond favorably to triptans. In a meta-analysis of 53 trials, up to a third of all people with migraine and 40% of all migraine attacks did not respond to triptans (Ferrari et al., Lancet, Vol. 358:1668-1675, 2001).
Migraine prophylaxis is an area of large unmet medical need. Approximately 40% of the migraine patient population would benefit from preventive therapy (Lipton et al., Neurology, Vol. 68:343-349, 2007). However, only approximately 12% of patients receive any preventive therapy due in part to limited efficacy and significant tolerability and safety issues with available preventive therapies. Topiramate, an anticonvulsant that blocks voltage-dependent sodium channels and certain glutamate receptors (AMPA-kainate), is the medication most often used for migraine prophylaxis in the United States. Topiramate is the only migraine prophylactic agent with demonstrated efficacy in both episodic and chronic migraine patients through randomized placebo-controlled trials (Diener et al., Cephalalgia, Vol. 27:814-823, 2007; Silberstein et al., Headache, Vol. 47:170-180, 2007). However, approximately 50% of patients fail to respond to topiramate and it is poorly tolerated. Common adverse events associated with topiramate treatment include paresthesia, anorexia, and cognitive adverse events, including psychomotor slowing, somnolence, language difficulties, and difficulties with memory and concentration (Brandes et al., JAMA, Vol. 291:965-973, 2004; Adelman et al., Pain Med., Vol. 9:175-185 2008; Silberstein et al., Arch Neurol., Vol. 61:490-495, 2004). In an open-label, flexible-dose study, 20% of patients withdrew from topiramate because of adverse effects (Nelles et al., Headache, Vol. 49:1454-1465, 2009).
Thus, migraine sufferers have an urgent medical need for more effective and/or tolerable treatment options.